Our second baby is due the day after Christmas. DD is 2.5. Everything I read about how to prepare a toddler for a sibling says to keep their routine as consistent as possible. Well, having the baby at Christmas makes that pretty difficult. Daycare will be closed 12/25, 12/26, and 1/1/18, and MIL/FIL will be staying with us to help care for her and also to spend Christmas, and SIL+fiancee will also be with us for a good chunk of that, and there's the general chaos of all the presents and festivities and candy. So as far from regular routine as you can get, basically.
Ideas on how to smooth this out at all? She's incredibly excited for baby brother to arrive, but I know we're going to get some boundary testing and regressing and all that.